Differential silicon interface for dielectric slab waveguide

ABSTRACT

The present disclosure relates to an integrated chip having differential coupling elements that couple electromagnetic radiation having a frequency outside of the visible spectrum between a silicon substrate and a dielectric waveguide overlying the silicon substrate. In some embodiments, the integrated chip has a dielectric waveguide disposed within an inter-level dielectric (ILD) material overlying a semiconductor substrate. A differential driver circuit generates a differential signal having a first transmission signal component at a first output node and a complementary second transmission signal component at a second output node. A first transmission electrode located along a first side of the dielectric waveguide receives the first transmission signal component from the first output node, and a second transmission electrode located along a second side of the dielectric waveguide receives the complementary second transmission signal component from the second output node.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No. 14/483,247 filed on Sep. 11, 2014, the contents of which are incorporated by reference in their entirety.

BACKGROUND

Integrated optical waveguides are often used as components in integrated optical circuits, which integrate multiple photonic functions. Integrated optical waveguides are used to confine and guide light from a first point on an integrated chip (IC) to a second point on the IC with minimal attenuation. Generally, integrated optical waveguides provide functionality for signals imposed on optical wavelengths in the visible spectrum (e.g., between approximately 850 nm and approximately 1650 nm).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIGS. 1A-1B illustrate some embodiments of an integrated chip comprising an integrated dielectric waveguide.

FIG. 2 illustrates some embodiments of a cross-sectional view of an integrated chip comprising an integrated dielectric waveguide.

FIG. 3 illustrates some embodiments of a top-view of an integrated chip comprising an integrated dielectric waveguide having one or more tapered transitional regions.

FIG. 4 illustrates some embodiments of a top-view of an integrated chip comprising a plurality of integrated dielectric waveguides configured to convey electromagnetic radiation in parallel.

FIGS. 5A-5B illustrates some embodiments of integrated chips comprising an integrated dielectric waveguide disposed within a back-end-of-the-line (BEOL) metallization stack.

FIG. 6 illustrates some embodiments of an integrated chip comprising an integrated dielectric waveguide configured to convey a differential signal.

FIG. 7 illustrates some embodiments of an integrated chip comprising a differential driver circuit and a differential receiver circuit disposed within a silicon substrate.

FIGS. 8-10 illustrate three-dimensional views of some additional embodiments of an integrated chip comprising an integrated dielectric waveguide coupled to differential coupling elements.

FIG. 11 illustrates some embodiments of an integrated chip comprising a dielectric waveguide having differential coupling elements disposed within a BEOL metallization stack.

FIG. 12 illustrates a flow diagram of some embodiments of a method of forming an integrated chip comprising an integrated dielectric waveguide.

FIG. 13 illustrates a flow diagram of some embodiments of a method of forming an integrated chip comprising an integrated dielectric waveguide disposed within a BEOL metallization stack.

FIGS. 14-19 illustrate some embodiments of cross-sectional views showing a method of forming an integrated chip comprising an integrated dielectric waveguide.

FIG. 20 illustrates a flow diagram of some embodiments of a method of forming an integrated chip comprising a dielectric waveguide coupled to differential coupling elements.

FIGS. 21-26 illustrate some embodiments of cross-sectional views showing a method of forming an integrated chip comprising a dielectric waveguide coupled to differential coupling elements.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Integrated optical waveguides are often used in integrated optical circuits. Generally, an integrated optical waveguide consist of an optical medium having a high dielectric constant (i.e., a core), which is surrounded by a medium having a lower dielectric constant. Visible light that is injected into an end of the integrated optical waveguide (e.g., using a lens, a grating coupler or prism coupler) is guided along a length of the waveguide by way of total internal reflection due to the difference in dielectric constants between the core and the surrounding medium.

Because integrated optical waveguides are limited to transmitting electromagnetic radiation in the visible section of the electromagnetic spectrum (e.g., having a frequency on the order of approximately 10¹⁵), they face a number of drawbacks. For example, integrated optical waveguides are not able to directly interact with circuitry disposed within a silicon substrate since silicon is not a direct band-gap semiconductor material that generates photons. Furthermore, the bandwidth that can be transmitted by integrated optical waveguides is limited. Because of these drawbacks, data is often transferred on silicon substrates using metal transmission lines rather than integrated optical waveguides. However, at high frequencies metal transmission lines experience a high rate of loss over large distances.

Accordingly, the present disclosure relates to an integrated chip comprising coupling elements configured to couple electromagnetic radiation having a frequency outside of the visible spectrum from a silicon substrate into an integrated dielectric waveguide overlying the silicon substrate. In some embodiments, the integrated chip comprises a dielectric waveguide disposed within an inter-level dielectric (ILD) material overlying a semiconductor substrate. A first coupling element is configured to couple a first electrical signal generated by a driver circuit disposed within the semiconductor substrate to a first end of the dielectric waveguide as electromagnetic radiation having a frequency outside of the visible spectrum. A second coupling element is configured to couple the electromagnetic radiation from a second end of the dielectric waveguide to a second electrical signal. By coupling electromagnetic radiation having a frequency outside of the visible spectrum to and from the dielectric waveguide, the disclosed integrated chip is able to overcome a number of drawbacks of optical integrated waveguides.

FIG. 1A illustrates some embodiments of a block diagram showing a cross-sectional view of an integrated chip 100 comprising an integrated dielectric waveguide.

The integrated chip 100 comprises a semiconductor substrate 102. In various embodiments, the semiconductor substrate 102 may comprise any type of semiconductor body such as a semiconductor wafer or one or more die on a wafer, as well as any other type of semiconductor and/or epitaxial layers formed thereon and/or otherwise associated therewith. In some embodiments, the semiconductor substrate 102 may comprise an indirect band-gap material, such as silicon.

An inter-level dielectric (ILD) material 104 is disposed over the semiconductor substrate 102. In various embodiments, the ILD material 104 may comprise one or more dielectric layers. For example, the ILD material 104 may comprise one or more of a low-k dielectric layer, an ultra-low k (ULK) dielectric layer, and/or a silicon dioxide (SiO₂) layer. A dielectric waveguide 106 is disposed within the ILD material 104. The dielectric waveguide 106 comprises a dielectric material having a dielectric constant (i.e., permittivity) that is larger than that of the surrounding ILD material 104.

A driver circuit 108 and a receiver circuit 110 are disposed within the semiconductor substrate 102. The driver circuit 108 is coupled to a first coupling element 114 by way of a first interconnect 112 (e.g., transmission line). The driver circuit 108 is configured to generate a first electrical signal, which is coupled into the dielectric waveguide 106 as electromagnetic radiation by way of a first coupling element 114. In some embodiments, the first coupling element 114 may comprise a metal coupling element (e.g., a metal transmission line or micro-strip line). In some embodiments, the electromagnetic radiation will have a frequency that is outside of the visible spectrum.

The dielectric waveguide 106 is configured to convey the electromagnetic radiation along a length of the dielectric waveguide 106 to a second coupling element 118. The second coupling element 118 is configured to couple the electromagnetic radiation from the dielectric waveguide 106 as a second electrical signal that is provided to the receiver circuit 110 by way of a second interconnect 116 (e.g., transmission line). In some embodiments, the second coupling element 118 may comprise a metal coupling element (e.g., a metal transmission line or micro-strip line). By using the first and second coupling elements, 114 and 118, to couple signals into and out of the dielectric waveguide 106, integrated chip 100 is able to transmit electromagnetic radiation over a broad range of frequencies, thereby enabling the dielectric waveguide 106 to be used to transfer data signals over substrates comprising direct and indirect band-gap materials.

FIG. 1B illustrates some embodiments of a three-dimensional view 120 of an integrated chip comprising an integrated dielectric waveguide.

As shown in three-dimensional view 120, the dielectric waveguide 106 comprises a slab waveguide disposed over the semiconductor substrate 102. In some embodiments, the dielectric waveguide 106 may have a substantially rectangular cross section comprising a height h and a width w. In some embodiments, the height h may be in a range of between approximately 100 nm and approximately 2 um. In some embodiments, the width w may be in range of between approximately 5 to approximately 15 times the height h. In some embodiments, the dielectric waveguide 106 may have sloped sidewalls, which give the dielectric waveguide 106 an inverted trapezoidal cross-section (having a width that increases as the height increases).

In some embodiments, the dielectric waveguide 106 may comprise a dielectric constant (i.e., permittivity) of greater than or equal to approximately 4, while the ILD material 104 may have a dielectric constant of less than 4. The greater dielectric constant of the dielectric waveguide 106 causes electromagnetic radiation introduced into the dielectric waveguide 106 to be confined within the dielectric waveguide 106 by total internal reflection, so that the electromagnetic radiation is guided from the driver circuit 108 to the receiver circuit 110. In some embodiments, the dielectric waveguide 106 may comprise silicon nitride (SiN) or silicon carbide (SiC). In some embodiments, the ILD material 104 may comprise silicon dioxide (SiO₂). In other embodiments, the ILD material 104 may comprise a low-k dielectric material, such as fluorine-doped silicon dioxide, carbon-doped silicon dioxide, porous silicon dioxide, or a similar material.

FIG. 2 illustrates some embodiments of a cross-sectional view of an integrated chip 200 comprising an integrated dielectric waveguide.

The integrated chip 200 comprises a silicon substrate 202 comprising a driver circuit 204 and a receiver circuit 206. The driver circuit 204 comprises a first MOS transistor having a first source region (S₁), a first drain region (D₁), and a first gate region (G₁) coupled to an input signal IN. The receiver circuit 206 comprises a second MOS transistor having a second source region (S₂), a second drain region (D₂), and a second gate region (G₂) coupled to the second coupling element 210.

During operation, the driver circuit 204 is configured to generate a first electrical signal S₁ at the first drain region (D₁) based upon the input signal IN. Since silicon is not a direct band-gap material, the first electrical signal S₁ generated by the driver circuit 202 has a frequency that is not in the visible spectrum (since silicon is an indirect band-gap material, the energy released during electron recombination with a hole is converted primarily into phonons, in contrast to direct band-gap materials that generate photons in the optical spectrum). The first electrical signal S₁ causes the first upper electrode 208 b to generate an electric field that extends outward from the first upper electrode 208 b, through the dielectric waveguide 106, to the first lower electrode 208 a. The electric field causes electromagnetic radiation corresponding to the first electrical signal S₁ to be coupled into the dielectric waveguide 106.

The coupled electromagnetic radiation is guided by the dielectric waveguide 106 to the second coupling element 210. The second coupling element 210 is configured to couple the electromagnetic radiation from the dielectric waveguide 106 to second electrical signal S₂, equivalent to the first electrical signal S₁, which is provided to the second gate region (G₂) of the receiver circuit 206.

While the first and second electrical signals, S₁ and S₂, may have a frequency that is lower than that of the visible spectrum, they can provide for a large data transfer rate due to the wide bandwidth of electromagnetic radiation that can be transmitted by the dielectric waveguide 106. For example, the dielectric waveguide 106 may provide for a bandwidth that is more than ten times larger than that of the visible spectrum, resulting in data transfer rates of that can exceed 10 gigabits/s. Such data transfer rates can provide for ultra-high-speed (UHS) interconnect on silicon substrates and/or on packages containing silicon substrates at high frequencies that experience high loss for transmission lines.

In some embodiments, the first coupling element 208 may comprise a first pair of metal structures (e.g., a micro-strips) disposed on opposing sides of the dielectric waveguide 106. For example, the first coupling element 208 may comprise a first lower electrode 208 a (e.g., within a first metal interconnect layer) disposed along a bottom surface of the dielectric waveguide 106 and a first upper electrode 208 b (e.g., within a second metal interconnect layer) disposed along a top surface of the dielectric waveguide 106. The first lower electrode 208 a is connected to a first ground terminal 209 a, while the first upper electrode 208 b is connected to the driver circuit 204 by way of a first metal transmission line 207. The first metal transmission line 207 provides for a wide bandwidth transmission of signals from the driver circuit 204 to the first upper electrode 208 b. In some embodiments, the first upper electrode 208 b may be comprised within the first metal transmission line 207.

The second coupling element 210 may comprise a second pair of metal structures disposed on opposing sides of the dielectric waveguide 106. For example, the second coupling element 210 may comprise a second lower electrode 210 a (e.g., within the first metal interconnect layer) disposed along the bottom surface of the dielectric waveguide 106 and a second upper electrode 210 b (e.g., within the second metal interconnect layer) disposed along the top surface of the dielectric waveguide 106. The second lower electrode 210 a is connected to a second ground terminal 209 b, while the second upper electrode 210 b is connected to the receiver circuit 206 by way of a second metal transmission line 211. The first pair of metal structures is laterally separated from the second pair of metal structures by a space S, so that the lower electrodes, 208 a and 210 a, and the upper electrodes, 208 b and 210 b, are non-continuous along a length of the dielectric waveguide 106. In some embodiments, the space S may be on the order of microns to tens of millimeters.

In some embodiments, a grounded shielding element 212 is vertically positioned between the dielectric waveguide 106 and the silicon substrate 202. The grounded shielding element 212 is configured to shield the dielectric waveguide 106 from interference due to signals generated within the silicon substrate 202, and vice versa. By shielding the dielectric waveguide 106 from interference due to signals generated within the silicon substrate 202, noise from the silicon substrate 202 will not be coupled into the dielectric waveguide 106, thereby improving performance of the dielectric waveguide 106.

FIG. 3 illustrates some embodiments of a top-view of an integrated chip 300 comprising an integrated dielectric waveguide having one or more tapered transitional regions, 312 and/or 314.

Integrated chip 300 comprises a first coupling element 302 and a second coupling element 304, respectively comprising micro-strip lines, 306 and 308, disposed over a dielectric waveguide 310. The micro-strip lines, 306 and 308, are configured to couple energy into and out of the dielectric waveguide 310, as described above.

In some embodiments, the dielectric waveguide 310 may comprise one or more tapered ends having widths w (along direction 316) that gradually decrease (e.g., from a first width to a second narrower width) over a length (along direction 318) of a transition region. For example, dielectric waveguide 310 comprises a first tapered end, having a width that decreases over a first transition region 312, and a second tapered end having a width that decreases over a second transition region 314.

The tapered ends of the dielectric waveguide 106 are configured to increase efficiency by which electromagnetic radiation is coupled between the micro-strip lines, 306 and/or 308, and the dielectric waveguide 310 by reducing the reflection of radiation between the micro-strip lines, 306 and/or 308, and the dielectric waveguide 310. For example, the tapered transitional region changes the angle at which electromagnetic radiation interacts with sidewalls of the dielectric waveguide 106, thereby increase the coupling of electromagnetic radiation between the micro-strip lines, 306 and/or 308, and the dielectric waveguide 310 (since total internal reflection is a function of an angle at which electromagnetic radiation is incident upon a surface).

In some embodiments, the micro-strip lines, 306 and 308, can also or alternatively have tapered widths, to further increase coupling efficiency between the first and second coupling elements, 302 and 304, and the dielectric waveguide 310. In such embodiments, the micro-strip lines, 306 and 308, have widths that decrease (e.g., from a first width to a second narrower width) over the transition regions, 312 and 314. In some embodiments, the tapered widths of the micro-strip lines, 306 and 308, may be different in length (i.e., have different sized transitional regions) than the tapered widths of a dielectric waveguide 106.

FIG. 4 illustrates some embodiments of a top-view of an integrated chip 400 comprising a plurality of an integrated dielectric waveguides configured to convey electromagnetic radiation in parallel.

Integrated chip 400 comprises a plurality of dielectric waveguides 408 a-408 c disposed between a driver circuit 402 and a receiver circuit 414. In some embodiments, the plurality of dielectric waveguides 408 a-408 c may be physically arranged in parallel to one another. In some embodiments, the plurality of dielectric waveguides 408 a-408 c may abut one another. In other embodiments, the plurality of dielectric waveguides 408 a-408 c may be spatially separated from one another.

The driver circuit 402 comprises a plurality of separate driver elements, 402 a-402 c, which are configured to respectively generate a first electrical signal S₁′. The first electrical signal S₁′ is provided in parallel to micro-strip lines 404 a-404 c, which couple the first electrical signal S₁′ as electromagnetic radiation into the plurality of dielectric waveguides 408 a-408 c, which convey the signal in parallel. Since the first electrical signal S₁′ is transmitted in parallel, smaller amplitude signals can be conveyed by each of the plurality of dielectric waveguides 408 a-408 c, thereby further decreasing loss between the micro-strips 404 a-404 c and the plurality of dielectric waveguides 408 a-408 c (e.g., the smaller amplitude signals S₁′ output by the plurality of driver elements, 402 a-402 c, and received by the plurality of receiver elements 414 a-414 c will cause coupling elements 406 and 410 to experience less loss).

FIG. 5A illustrates some embodiments of a cross-sectional view of an integrated chip 500 comprising an integrated dielectric waveguide disposed within a back-end-of-the-line (BEOL) metallization stack.

The integrated chip 500 comprises a driver circuit 502 and a receiver circuit 504 disposed within a silicon substrate 202. The driver circuit 502 comprises a first MOS transistor having a first source region (S) separated from a first drain region (D) by a first channel region. A first gate region overlies the first channel region. The receiver circuit 504 comprises a second MOS transistor having a second source region (S) separated from a second drain region (D) by a second channel region. A second gate region overlies the second channel region.

The BEOL metallization stack comprises a plurality of metal interconnect layers disposed within an ILD material overlying the silicon substrate 202. In some embodiments, the BEOL metallization stack may alternate between metal wire layers M1-M3 (configured to provide for lateral connections) and via layers V0-V2 (configured to provide for vertical connections). In some embodiments, a first via layer V0 may comprise tungsten (W), while the remaining metal interconnect layers, V1-V2 and M1-M3, may comprise copper (Cu) and/or aluminum (Al)

A first coupling element 520 comprises a first lower electrode 520 a disposed within a second metal wire layer M2 and a first upper electrode 520 b disposed within a third metal wire layer M3. The first lower electrode 520 a is grounded, while the first upper electrode 520 b is coupled to the first drain region of the first MOS transistor by way of a plurality of metal interconnect layers (V2, M2, V1, M1, and V0). The second coupling element 522 comprises a second lower electrode 522 a disposed within the second metal wire layer M2 and a second upper electrode 522 b disposed on the third metal wire layer M3. The second lower electrode 522 a is grounded, while the second upper electrode 522 b is coupled to the second gate region of the second MOS transistor by way of a plurality of metal interconnect layers (V2, M2, V1, M1, and V0). In some embodiments, the dielectric waveguide 514 comprises a dielectric material disposed within a second via layer V2 vertically disposed between the second metal wire layer M2 and the third metal wire layer M3

In some embodiments, a shielding element 524 is vertically arranged between the dielectric waveguide 514 and the silicon substrate 202. The shielding element 524 comprises a plurality of grounded metal wires 524 a-524 d arranged in parallel. In some embodiments, the plurality of grounded metal wires 524 a-524 d are disposed on a first metal wire layer M1. The shielding element 524 is configured to shield the dielectric waveguide 514 from the silicon substrate 202, which is lossy, thereby preventing loss in signals transmitted by the dielectric waveguide 514.

Although FIG. 5A illustrates the dielectric waveguide 514 as being on a second via layer V1 vertically disposed between first and second coupling elements, 520 and 522, located on the second and third metal wire layers, M2 and M3, it will be appreciated that the disclosed dielectric waveguide 514 is not limited to such positions within the BEOL metallization stack. Rather, the dielectric waveguide 514 and the first and second coupling elements, 520 and 522, may be disposed at different positions within the BEOL metallization stack.

FIG. 5B illustrates a three-dimensional view of some alternative embodiments of an integrated chip 526 comprising an integrated dielectric waveguide disposed within a BEOL metallization stack. Integrated chip 526 comprises lower electrodes, 520 a and 522 a, and upper electrodes, 520 b and 522 b, which extend to positions below and above the dielectric waveguide 514 from opposite sides.

FIG. 6 illustrates some embodiments of a three-dimensional (3D) view of an integrated chip 600 having a dielectric waveguide configured to convey a differential signal. The use of a differential signal may provide for a number of performance advantages over single ended signals. For example, the differential signal is more robust against interference (e.g., from external circuits) and generate less even harmonics than a single ended signal.

The integrated chip 600 comprises a differential driver circuit 602 and a differential receiver circuit 612 disposed within a silicon substrate 202. The differential driver circuit 602 is configured to receive a first input signal S_(IN+) and a complimentary second input signal S_(IN−) (i.e., which is symmetric to the first input signal S_(IN+)), and based thereupon to generate differential signal having a first transmission signal component S₁ at a first output node OUT₁ and a complementary second transmission signal component S₂ (i.e., a second signal having a complementary value to the first transmission signal component S₁) at a second output node OUT₂.

The first transmission signal component S₁ and the complementary second transmission signal component S₂ are provided to a differential transmission coupling element 605 by way of transmission lines 603 a and 603 b. The differential transmission coupling element 605 comprises a first transmission electrode 604 and a second transmission electrode 606. The first transmission electrode 604 and the second transmission electrode 606 are conductive structures (e.g., metal structures) that are symmetric (i.e., the shapes/patterns of the electrodes mirror images) about a dielectric waveguide 106. The first transmission electrode 604 is located along a first side of the dielectric waveguide 106 and is configured to receive the first transmission signal component S₁ from the differential driver circuit 602. The second transmission electrode 606 is located along a second side of the dielectric waveguide 106 and is configured to receive the complementary second transmission signal component S₂ from the differential driver circuit 602.

The dielectric waveguide 106 is configured to transmit the first signal and second transmission signals, S₁ and S₂, to a differential receiver coupling element 609 comprising a first receiver electrode 608 and a second receiver electrode 610 located on opposite sides of the dielectric waveguide 106. The first receiver electrode 608 and the second receiver electrode 610 are symmetric (i.e., the shapes/patterns of the electrodes mirror images) about the dielectric waveguide 106. The first receiver electrode 608 and a second receiver electrode 610 are configured to extract a first received signal component S₁′ and a second received signal component S₂′ from the dielectric waveguide 106. The first received signal component S₁′ is provided to a first input node IN₁ of the differential receiver circuit 612 by way of a first transmission line 611 a. The second received signal component S₂′ is provided to a second input node IN₂ of the differential receiver circuit 612 by way of a second transmission line 611 b. The differential receiver circuit 612 is configured to generate output signals S_(out+) and S_(out−) from the received signal components, thereby conveying a differential signal over the dielectric waveguide 106.

FIG. 7 illustrates some embodiments of a cross-sectional view of an integrated chip 700 comprising a differential driver circuit 702 and a differential receiver circuit 704 disposed within a silicon substrate 202.

The differential driver circuit 702 is configured to generate a differential signal having a first transmission signal component S₁ and a complementary second transmission signal component S₂. In some embodiments, the differential driver circuit comprises a first MOS transistor 702 a and a second MOS transistor 702 b. The first MOS transistor 702 a comprises a first source region (S₁) connected to a ground terminal, a first drain region (D₁) connected to a first output node and to a drain bias voltage V_(DD1) (via RF chock 702 c), and a first gate region (G₁) connected to a first input signal S_(IN+) and to a gate bias voltage V_(DD2) (via RF chock 702 d). The second MOS transistor 702 b comprises a second source region (S₂) connected to the ground terminal, a second drain region (D₂) connected to a second output node and to drain bias voltage V_(DD1) (via RF chock 702 c), and a second gate region (G₂) connected to a second input signal S_(IN−) and to gate bias voltage V_(DD2) (via RF chock 702 d).

During operation, the first input signal S_(IN+) will turn on the first MOS transistor 702 a when the second input signal S_(IN−) turns off the second MOS transistor 702 b, or vice versa. When turned on, the first MOS transistor 702 a will drive the first transmission signal component S₁ low, while the turned off second MOS transistor 702 b will drive the complementary second transmission signal component S₂ high. Since silicon is not a direct band-gap material, the first and second transmission signal components, S₁ and S₂ generated by the differential driver circuit 702 have a frequency that is not in the visible spectrum (since silicon is an indirect band-gap material, the energy released during electron recombination with a hole is converted primarily into phonons, in contrast to direct band-gap materials that generate photons in the optical spectrum). The first and second transmission signal components, S₁ and S₂, cause differential transmission coupling element 605 to generate an electric field that is coupled into the dielectric waveguide 106.

The coupled electromagnetic radiation is guided by the dielectric waveguide 106 to differential receiver coupling element 609, which has a first receiver electrode 608 and a second receiver electrode 610. The differential receiver coupling element 609 is configured to couple the electromagnetic radiation from the dielectric waveguide 106 to first and second received signal components, S_(1′) and S_(2′), which are equivalent to the first and second transmission signal components, S₁ and S₂. The first and second received signal components, S_(1′) and S_(2′), are provided to a differential receiver circuit 704. In some embodiments, the differential receiver circuit 704 comprises a third MOS transistor 704 a and a fourth MOS transistor 704 b. The third MOS transistor 704 a comprises a third source region (S₃) connected to a ground terminal, a third gate region (G₃) connected to the first receiver electrode 608 and to a gate bias voltage V_(DD3) (via RF chock 704 c), and a third drain region (D₃) connected to drain bias voltage V_(DD4) (via RF chock 704 d) and configured to provide a first output signal S_(OUT+). The fourth MOS transistor 704 b comprises a fourth source region (S₄) connected to a ground terminal, a fourth gate region (G₄) connected to the second receiver electrode 610 and to gate bias voltage V_(DD3) (via RF chock 704 c), and a fourth drain region (D₄) connected to drain bias voltage V_(DD4) (via RF chock 704 d) and configured to provide a second output signal S_(OUT−).

Although MOS transistors 704 a-704 d are illustrated as single transistor devices, it will be appreciated that the MOS transistors may comprise an array of transistors comprising a plurality of transistor devices (e.g., FinFET devices) arranged in parallel. For example, first MOS transistor 702 a may comprise hundreds or transistor devices. Furthermore, it will be appreciated that the differential driver circuit 702 and the differential receiver circuit 704 illustrated in FIG. 7 are non-limiting examples of differential circuits that may be used to send and/or receive differential signals. In other embodiments, alternative differential circuits for high speed CMOS applications, known to one of ordinary skill in the art, may be used to generate or receive a differential signal.

FIG. 8 illustrates a three-dimensional view of some embodiments of an integrated chip 800 comprising an integrated dielectric waveguide coupled to differential coupling elements.

The integrated chip 800 comprises a differential transmission coupling element comprising a first plurality of transmission electrodes 804 disposed along a lower surface of a dielectric waveguide 106 and a second plurality of transmission electrodes 806 disposed along an upper surface of the dielectric waveguide 106. The first plurality of transmission electrodes 804 comprise a plurality of tapered shapes 804 a-804 c interconnected by a conductive line 805. The second plurality of transmission electrodes 806 comprise a plurality of tapered shapes 806 a-806 c interconnected by conductive line 807. In some embodiments, the plurality of tapered shapes, 804 a-804 c and 806 a-806 c, may comprise triangular shapes. The first plurality of transmission electrodes 804 are symmetric with respect to the second plurality of transmission electrodes 806, such that the shapes/patterns of the first and second plurality of transmission electrodes, 804 and 806, are mirror images.

The first plurality of transmission electrodes 804 are coupled to a first output of a differential driver circuit 802 (via transmission line 803 a) configured to provide a first transmission signal component S₁ to each of the first plurality of transmission electrodes 804. The second plurality of transmission electrodes 806 are coupled to a second output of the differential driver circuit 802 (via transmission line 803 b) configured to provide a second transmission signal component S₂ to each of the second plurality of transmission electrodes 806. Since the first and second transmission signal components, S₁ and S₂, drive each of the transmission electrodes 804 and 806, the electromagnetic signals output from each of the electrodes will be coherent, thereby constructively interfering with one another within the dielectric waveguide 106 and improving the strength of the electromagnetic signal transmitted within the dielectric waveguide 106.

The integrated chip 800 further comprises a differential receiver coupling element comprising a first plurality of receiver electrodes 808 disposed along a lower upper surface of the dielectric waveguide 106 and a second plurality of receiver electrodes 810 disposed along an upper surface of the dielectric waveguide 106. The first and second plurality of receiver electrodes, 808 and 810, comprise a plurality of tapered shapes. The first plurality of receiver electrodes 808 are configured to provide a first received signal component S_(1′) to a first input of a differential receiver circuit 812, and the second plurality of receiver electrodes 810 are configured to provide a second received signal component S_(2′) to a second input of the differential receiver circuit 812.

FIG. 9 illustrates a three-dimensional view of some embodiments of an integrated chip 900 comprising an integrated dielectric waveguide coupled to differential coupling elements.

The integrated chip 900 comprises a differential transmission coupling element comprises a first plurality of transmission electrodes 902 disposed along a lower surface of a dielectric waveguide 106 and a second plurality of transmission electrodes 904 disposed along an upper surface of the dielectric waveguide 106. The first and second plurality of transmission electrodes, 902 and 904, respectively comprise electrodes having different sizes. For example, transmission electrode 902 b extends to a distance d past the edge of transmission electrodes 902 a and 902 c. The different sizes of the different transmission electrodes 904 allows for the electrodes to focus radiation at different locations within the dielectric waveguide 106. For example, the larger size of transmission electrode 902 b will cause radiation to be focused into a center of the dielectric waveguide 106 (i.e., radiation within the dielectric waveguide 106 will have an amplitude that is greater at the center of the waveguide than at the edges of the waveguide).

The integrated chip 900 further a differential receiver coupling element comprises a first plurality of receiver electrodes 906 disposed along a lower surface of the dielectric waveguide 106 and a second plurality of receiver electrodes 908 disposed along an upper surface of the dielectric waveguide 106. The first and second plurality of receiver electrodes, 906 and 908, respectively comprise electrodes having different sizes.

FIG. 10 illustrates a three-dimensional view of some embodiments of an integrated chip comprising an integrated dielectric waveguide coupled to differential coupling elements.

Integrated chip 1000 comprises a differential driver circuit 1002 and a differential receiver circuit 1010. The differential driver circuit 1002 is connected to a first plurality of transmission electrodes 1004 disposed below a dielectric waveguide 106 and a second plurality of transmission electrodes 1006 disposed above the dielectric waveguide 106. The first plurality of transmission electrodes 1004 are electrically de-coupled, and the second plurality of transmission electrodes 1006 are electrically decoupled.

The differential driver circuit 1002 comprises a plurality of separate differential driver circuits 1002 a-1002 d. In some embodiments, each of the plurality of separate differential driver circuits 1002 a-1002 d may comprise a separate array of transistor devices arranged in parallel. The separate differential driver circuits 1002 a-1002 d are configured to drive one of the first plurality of transmission electrodes 1004 and one of the second plurality of transmission electrodes 1006, such that each of the first or second plurality of transmission electrodes, 1004 and 1006, is driven by a separate driver circuit. For example, in some embodiments, the separate differential driver circuits 1002 a-1002 d respectively comprise a first transistor having a first gate coupled to a first input signal S_(IN+) and a first drain coupled to one of the first plurality of transmission electrodes 1004, and a second transistor device having a second gate coupled to a second input signal S_(IN−) and a second drain coupled to one of the second plurality of transmission electrodes 1006.

Similarly, the differential receiver circuit 1010 comprises a plurality of separate differential receiver circuits 1010 a-1010 d. The separate differential receiver circuits 1010 a-1010 d are configured to receive differential receiver signals from one of a first plurality of receiver electrodes 1012 and one of a second plurality of receiver electrodes 1014. For example, in some embodiments, the separate differential receiver circuits 1010 a-1010 d respectively comprise a first transistor device having a first gate coupled to one of the first plurality of receiver electrodes 1012 and a first drain coupled to a first output signal S_(OUT+), and a second transistor device having a second gate coupled to one of the second plurality of transmission electrodes 1006 and a second drain coupled to a second output signal S_(OUT−).

FIG. 11 illustrates a three-dimensional view of some embodiments of an integrated chip 1100 comprising a dielectric waveguide having differential coupling elements disposed within a BEOL metallization stack.

The integrated chip 1100 comprises a differential driver circuit 1102 and a differential receiver circuit 1104 disposed within a silicon substrate 202. The differential driver circuit 1102 comprises a first MOS transistor 1102 a having a first source region (S₁) separated from a first drain region (D₁) by a first channel region. A first gate region (G₁) overlies the first channel region. The differential driver circuit 1102 further comprises a second MOS transistor 1102 b having a second source region (S₂) separated from a second drain region (D₂) by a second channel region. A second gate region (G₂) overlies the second channel region. The differential receiver circuit 1104 comprises a third MOS transistor 1104 a having a third source region (S₃) separated from a third drain region (D₃) by a third channel region. A third gate region (G₃) overlies the third channel region. The differential receiver circuit 1104 further comprises a fourth MOS transistor 1104 b having a fourth source region (S₄) separated from a fourth drain region (D₄) by a fourth channel region. A fourth gate region (G₄) overlies the fourth channel region.

A differential transmission coupling element 520′ comprises a first transmission electrode 520 a′ disposed within a second metal wire layer M2 and a second transmission electrode 520 b′ disposed within a third metal wire layer M3. The first transmission electrode 520 a′ is coupled to the first drain region (D₁) of the first MOS transistor 1102 a by way of a plurality of metal interconnect layers (V2, M2, V1, M1, and V0), while the first upper electrode 520 b′ is coupled to the second drain region (D₂) of the second MOS transistor 1102 b by way of a plurality of metal interconnect layers (V2, M2, V1, M1, and V0).

A differential receiver coupling element 522′ comprises a first receiver electrode 522 a′ disposed within the second metal wire layer M2 and a second receiver electrode 522 b′ disposed on the third metal wire layer M3. The first receiver electrode 522 a′ is coupled to the third gate region (G₃) of the third MOS transistor 1104 a by way of a plurality of metal interconnect layers (V2, M2, V1, M1, and V0), while the second receiver electrode 522 b′ is coupled to the fourth gate region (G₄) of the fourth MOS transistor by way of a plurality of metal interconnect layers (V2, M2, V1, M1, and V0).

FIG. 12 illustrates a flow diagram of some embodiments of a method 1200 of forming an integrated chip comprising an integrated dielectric waveguide.

While disclosed methods (e.g., methods 1200, 1300, and 2000) are illustrated and described herein as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events are not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

At 1202, a semiconductor substrate is provided comprising a driver circuit and a receiver circuit. In some embodiments, the semiconductor substrate may comprise an indirect band-gap semiconductor material, such as silicon.

At 1204, a dielectric waveguide is formed at a position surrounded by an (inter-level dielectric) ILD material overlying the semiconductor substrate.

At 1206, first and second coupling elements are formed on opposing ends of the dielectric waveguide. The first and second coupling elements comprise metal structures disposed on opposing sides of the dielectric waveguide, which are configured to respectively couple a first electrical signal from the driver circuit to the dielectric waveguide as electromagnetic radiation that is outside of the visible spectrum of light and to couple electromagnetic radiation from the dielectric waveguide to a second electrical signal that is provided to the receiver circuit.

FIG. 13 illustrates a flow diagram of some embodiments of a method 1300 of forming an integrated chip comprising an integrated dielectric waveguide disposed within a back-end-of-the line (BEOL) metallization stack.

At 1302, a silicon substrate comprising a driver circuit and a receiver circuit is provided. In some embodiments, the driver circuit and the receiver circuit comprise MOS transistors disposed within the silicon substrate.

At 1304, a first (inter-level dielectric) ILD layer overlying the silicon substrate is patterned to form a first plurality of openings.

At 1306, a first metal material is formed within the first plurality of openings to form a first via layer contacting the driver and receiver circuits.

At 1308, a second ILD layer overlying the first ILD layer is patterned to form a second plurality of openings comprising a plurality of shielding element openings and a first plurality of metal wire trenches.

At 1310, a second metal material is formed within the plurality of shielding element openings and the first plurality of metal wire trenches. Forming the second metal material within the plurality of shielding element openings forms a shielding element comprising a plurality of grounded metal wires within the second ILD layer, which are arranged in parallel.

At 1312, a third ILD layer overlying the second ILD layer is patterned to form a third plurality of openings. The third plurality of openings comprise a first lower electrode opening and a second lower electrode opening. The first and second lower electrode openings are laterally separated from one another.

At 1314, a third metal material is formed within the first and second lower electrode openings to form first and second lower electrodes within the third ILD layer.

At 1316, a fourth ILD layer overlying the third ILD layer is patterned to form a dielectric waveguide opening. The dielectric waveguide opening has a first end that exposes the first lower electrode and a second end that exposes the second lower electrode.

At 1318, a dielectric material is formed within the dielectric waveguide opening to form a dielectric waveguide within the fourth ILD layer. The dielectric material has a greater dielectric constant than that of surrounding ILD layers.

At 1320, the fourth ILD layer is patterned to form a second plurality of via holes within the fourth ILD layer.

At 1322, a fourth metal material is formed within the second plurality of via holes.

At 1324, a fifth ILD layer overlying the fourth ILD layer is patterned to form a first upper electrode opening and a second upper electrode opening. The first upper electrode opening and the second upper electrode opening are laterally separated from one another, and expose opposing ends of the dielectric waveguide.

At 1326, a fifth metal material is formed within the first and second upper electrode openings to form first and second upper electrodes within the fifth ILD layer.

FIGS. 14-19 illustrate some embodiments of cross-sectional views showing a method of forming an integrated chip comprising an integrated dielectric waveguide. Although FIGS. 14-19 are described in relation to method 1300, it will be appreciated that the structures disclosed in FIGS. 14-19 are not limited to such a method, but instead may stand alone as structures independent of the method.

FIG. 14 illustrates some embodiments of a cross-sectional view 1400 of an integrated chip corresponding to act 1302.

As shown in cross-sectional view 1400, a silicon substrate 202 is provided. The silicon substrate 202 comprises a driver circuit 502 and a receiver circuit 504. In some embodiments, the driver circuit 502 and the receiver circuit 504 comprise MOS transistors disposed within the silicon substrate 202.

FIG. 15 illustrates cross-sectional views, 1500 and 1506, of an integrated chip corresponding to acts 1304-1306.

As shown in cross-sectional view 1500, a first ILD layer 506 is formed over the silicon substrate 202. The first ILD layer 506 may comprise a low-k dielectric layer deposited by way of a vapor deposition technique (e.g., physical vapor deposition, chemical vapor deposition, etc.). In some embodiments, the first ILD layer 506 may have a dielectric constant that is less than 3.9.

The first ILD layer 506 is selectively exposed to a first etchant 1502. The first etchant 1502 is configured to selectively etch the first ILD layer 506 to form a first plurality of openings 1504 extending through the first ILD layer 506. The first plurality of openings 1504 expose a drain of the driver circuit 502 and the receiver circuit 504. In some embodiments, the first etchant 1502 may comprise a dry etchant have an etching chemistry comprising a fluorine species (e.g., CF₄, CHF₃, C₄F₈, etc.). In some embodiments, the etching chemistry may further comprise oxygen or hydrogen, for example. In other embodiments, the first etchant 1502 may comprise a wet etchant comprising hydroflouric acid (HF).

As shown in cross-sectional view 1506, a first metal material 1508 is formed within the first plurality of openings 1504. In some embodiments, the first metal material 1508 may be formed by way of a vapor deposition technique. In some embodiments, the first metal material 1508 may comprise tungsten (W). In some embodiments, a diffusion barrier layer (not shown) may be deposited into the first plurality of openings 1504 prior to forming the first metal material 1508. In various embodiments, the diffusion barrier layer may comprise titanium nitride (TiN), tantalum nitride (TaN), hafnium nitride (HfN), etc.

FIG. 16 illustrates cross-sectional views, 1600 and 1608, of an integrated chip corresponding to acts 1308-1310.

As shown in cross-sectional view 1600, a second ILD layer 508 (e.g., a low-k dielectric layer) is formed over the first ILD layer 506 (e.g., by way of a vapor deposition technique). The second ILD layer 508 is selectively exposed to a second etchant 1602 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to selectively etch the second ILD layer 508 to form a second plurality of openings comprising a first plurality of via openings 1604 and a plurality of shielding element openings 1606 laterally disposed from the plurality of via openings 1604. The plurality of shielding element openings 1606 comprise metal trenches extending in parallel to one another.

As shown in cross-sectional view 1608, a second metal material 1610 is formed in the first plurality of via openings 1604 and the plurality of shielding element openings 1606. In some embodiments, a deposition process may be used to form a seed layer within the first plurality of via openings 1604 and the plurality of shielding element openings 1606. A subsequent plating process (e.g., an electroplating process, an electro-less plating process) may be used to form the second metal material to a thickness that fills the first plurality of via openings 1604 and the plurality of shielding element openings 1606. In some embodiments, the second metal material 1610 may comprise copper (Cu). A chemical mechanical polishing (CMP) process may be used to remove excess of the second metal material 1610 from a top surface of the second ILD layer 508.

FIG. 17 illustrates cross-sectional views, 1700 and 1702, of an integrated chip corresponding to acts 1312-1314.

As shown in cross-sectional view 1700, a third ILD layer 510 is formed onto the second ILD layer 508. The third ILD layer 510 is selectively exposed to a third etchant 1702 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the third ILD layer 510 to from a third plurality of openings 1704. In some embodiments, the third plurality of openings 1704 comprise a via hole, and an overlying metal wire trench. The via holes vertically extending from a bottom surface of the third ILD layer 510 to a bottom surface of the metal trenches, which extend to a top surface of the third ILD layer 510.

As shown in cross-sectional view 1706, a third metal material 1708 is formed in the third plurality of openings 1704 to form a second via layer V1 and an overlying second metal wire layer M2. The second metal wire layer M2 comprises a first lower electrode 520 a and a second lower electrode 522 a. The first lower electrode 520 a is laterally separated from the second lower electrode 522 a by way of the third ILD layer 510. In some embodiments, the third metal material 1708 (e.g., copper) may be deposited by way of a deposition process, a subsequent plating process, and a CMP process, as described above.

Although FIG. 17 illustrates the formation of the second via layer V1 and second metal wire layer M2 using a dual damascene process, one of ordinary skill in the art will appreciate that the in alternative embodiments, the second via layer V1 and the second metal wire layer M2 may be formed using a single damascene process. In such embodiments, a first dielectric layer is selectively etched to form via holes, which are subsequently filled. A second dielectric layer is then formed over the first dielectric layer. The second dielectric layer is selectively etched to form metal trenches.

FIG. 18 illustrates some embodiments of cross-sectional views, 1800 and 1802, of an integrated chip corresponding to acts 1316-1322.

As shown in cross-sectional view 1800, a fourth ILD layer 512 is formed over the third ILD layer 510. The fourth ILD layer 512 is selectively exposed to a fourth etchant 1802 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the fourth ILD layer 512 to form a dielectric waveguide opening 1804. The dielectric waveguide opening 1804 comprises an oblong opening that laterally extends from a first position overlying the first lower electrode 520 a to a second position overlying the second lower electrode 522 a.

As shown in cross-sectional view 1806, a dielectric material 1808 is formed within the dielectric waveguide opening 1804. The dielectric material 1808 comprises a higher dielectric constant than the surrounding ILD layers (e.g., ILD layer 510 and 512). In some embodiments, the dielectric material 1808 may be formed by way of a vapor deposition technique (e.g., PVD, CVD, PE-CVD, etc.) to a thickness that fills the dielectric waveguide opening 1804. A chemical mechanical polishing (CMP) process may be used to remove excess of the dielectric material 1808 from a top surface of the fourth ILD layer 512.

As shown in cross-sectional view 1810, the fourth ILD layer 512 is selectively exposed to a fifth etchant 1812 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the fourth ILD layer 512 to from a second plurality of via holes 514. The second plurality of via holes 1814 comprise substantially round via openings disposed over an underlying metal layer (i.e., the via holes 1814 are predominately over the underlying second metal layer M2 so as to provide for contact between a subsequently formed via and the underlying second metal layer M2). The second plurality of via holes 1814 are laterally separated from the dielectric waveguide opening 1804 (i.e., the dielectric waveguide opening 1804 is disposed on a same vertical level as the second plurality of via holes 1814).

As shown in cross-sectional view 1816, a fourth metal material 1818 is formed within the second plurality of via holes 1814. In some embodiments, the fourth metal material 1818 (e.g., copper) may be deposited by way of a deposition process, a subsequent plating process, and a CMP process, as described above.

FIG. 19 illustrates some embodiments of cross-sectional views, 1900 and 1906, of an integrated chip corresponding to acts 1324-1326.

As shown in cross-sectional view 1900, a fifth ILD layer 518 is formed over the fourth ILD layer 512. The fifth ILD layer 518 is selectively exposed to a sixth etchant 1902 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the fifth ILD layer 518 to from a fourth plurality of openings 1904 comprising metal trenches that extend through the fifth ILD layer 518.

As shown in cross-sectional view 1906, a fifth metal material 1908 is formed in the fourth plurality of openings 1904. In some embodiments, the fifth metal material 1908 (e.g., copper) may be deposited by way of a deposition process, a subsequent plating process, and a CMP process, as described above. The fifth metal material 1908 forms a first upper electrode 520 b and a second upper electrode 522 b within a third metal wire layer M3. The first upper electrode 520 b is laterally separated from the second upper electrode 522 b by way of the fifth ILD layer 518.

FIG. 20 illustrates a flow diagram of some embodiments of a method 2000 of forming an integrated chip comprising a dielectric waveguide coupled to differential coupling elements.

At 2002, a differential driver circuit is formed within a silicon substrate. The differential driver circuit has a first output node configured to provide a first transmission signal component and a second output node configured to provide a complementary second transmission signal component. In some embodiments, the differential driver circuit comprises MOS transistors disposed within the silicon substrate.

At 2004, a differential receiver circuit is formed within the silicon substrate. The differential receiver circuit has a first input node configured to receive a first received signal component and a second input node configured to receive a complementary second received signal component. In some embodiments, the differential receiver circuit comprises MOS transistors disposed within the silicon substrate.

At 2006, a first metal material is formed within a first plurality of openings in a first ILD layer to form a first via layer contacting the first and second output nodes of the differential driver circuit and the first and second inputs nodes of the differential receiver circuit.

At 2008, a second metal material is formed within a second plurality of shielding element openings and a first plurality of metal wire trenches formed within a second ILD layer overlying the first ILD layer. Forming the second metal material within the plurality of shielding element openings forms a shielding element comprising a plurality of grounded metal wires within the second ILD layer, which are arranged in parallel.

At 2010, a third metal material is formed within a lower electrode openings within a third ILD layer to form a first transmission electrode coupled to the first output node and a first receiver electrode coupled to the first input node.

At 2012, a fourth ILD layer overlying the third ILD layer is patterned to form a dielectric waveguide opening. The dielectric waveguide opening has a first end that exposes the first transmission electrode and a second end that exposes the first receiver electrode.

At 2014, a dielectric material is formed within the dielectric waveguide opening to form a dielectric waveguide within the fourth ILD layer. The dielectric material has a greater dielectric constant than that of surrounding ILD layers.

At 2016, the fourth ILD layer is patterned to form a second plurality of via holes within the fourth ILD layer.

At 2018, a fourth metal material is formed within the second plurality of via holes.

At 2020, a fifth metal material is formed within upper electrode openings within a fifth ILD layer overlying the fourth ILD layer to form a second transmission electrode coupled to the second output node and a second receiver electrode coupled to the second input node. The second transmission electrode and the second receiver electrode are laterally separated from one another.

FIGS. 21-26 illustrate some embodiments of cross-sectional views showing a method of forming an integrated chip comprising an integrated dielectric waveguide coupled to differential coupling elements. Although FIGS. 21-26 are described in relation to method 2000, it will be appreciated that the structures disclosed in FIGS. 21-26 are not limited to such a method, but instead may stand alone as structures independent of the method.

FIG. 21 illustrates some embodiments of a cross-sectional view 2100 of an integrated chip corresponding to acts 2002-2004

As shown in cross-sectional view 2100, a silicon substrate 202 is provided. A differential driver circuit 1102 and a differential receiver circuit 1104 are formed within the silicon substrate 202. In some embodiments, the differential driver circuit 1102 may comprise first and second MOS transistors, 1102 a and 1102 b, and the differential receiver circuit 1104 may comprise first and second MOS transistors, 1104 a and 1104 b. In some embodiments, the MOS transistors may be formed by selectively implanting a dopant species into the silicon substrate 202 to form source and drain regions, and using lithography techniques to form gate structures over channel regions between the source and drain regions.

FIG. 22 illustrates cross-sectional views, 2200 and 2206, of an integrated chip corresponding to act 2006.

As shown in cross-sectional view 2200, a first ILD layer 506 is formed over the silicon substrate 202. The first ILD layer 506 may comprise a low-k dielectric layer deposited by way of a vapor deposition technique (e.g., physical vapor deposition, chemical vapor deposition, etc.). The first ILD layer 506 is selectively exposed to a first etchant 2202. The first etchant 2202 is configured to selectively etch the first ILD layer 506 to form a first plurality of openings 2204 extending through the first ILD layer 506. The first plurality of openings 2204 expose a drain of the driver circuit 502 and the receiver circuit 504. In various embodiments, the first etchant 2202 may comprise a dry etchant or a wet etchant.

As shown in cross-sectional view 2206, a first metal material 2208 is formed within the first plurality of openings 2204. In some embodiments, the first metal material 2208 may be formed by way of a vapor deposition technique. In some embodiments, the first metal material 2208 may comprise tungsten (W). In some embodiments, a diffusion barrier layer (not shown) may be deposited into the first plurality of openings 2204 prior to forming the first metal material 2208. In various embodiments, the diffusion barrier layer may comprise titanium nitride (TiN), tantalum nitride (TaN), hafnium nitride (HfN), etc.

FIG. 23 illustrates cross-sectional views, 2300 and 2308, of an integrated chip corresponding to act 2008.

As shown in cross-sectional view 2300, a second ILD layer 508 (e.g., a low-k dielectric layer) is formed over the first ILD layer 506 (e.g., by way of a vapor deposition technique). The second ILD layer 508 is selectively exposed to a second etchant 2302 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to selectively etch the second ILD layer 508 to form a second plurality of openings comprising a first plurality of via openings 2304 and a plurality of shielding element openings 2306 laterally disposed from the plurality of via openings 2304. The plurality of shielding element openings 2306 comprise metal trenches extending in parallel to one another.

As shown in cross-sectional view 2308, a second metal material 2310 is formed in the first plurality of via openings 2304 and the plurality of shielding element openings 2306. In some embodiments, a deposition process may be used to form a seed layer within the first plurality of via openings 2304 and the plurality of shielding element openings 2306. A subsequent plating process (e.g., an electroplating process, an electro-less plating process) may be used to form the second metal material to a thickness that fills the first plurality of via openings 2304 and the plurality of shielding element openings 2306. In some embodiments, the second metal material 2310 may comprise copper (Cu). A chemical mechanical polishing (CMP) process may be used to remove excess of the second metal material 2310 from a top surface of the second ILD layer 508.

FIG. 24 illustrates cross-sectional views, 2400 and 2402, of an integrated chip corresponding to act 2010.

As shown in cross-sectional view 2400, a third ILD layer 510 is formed onto the second ILD layer 508. The third ILD layer 510 is selectively exposed to a third etchant 2402 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the third ILD layer 510 to from a third plurality of openings 2404. In some embodiments, the third plurality of openings 2404 comprise a via hole, and an overlying metal wire trench. The via holes vertically extending from a bottom surface of the third ILD layer 510 to a bottom surface of the metal trenches, which extend to a top surface of the third ILD layer 510.

As shown in cross-sectional view 2406, a third metal material 2408 is formed in the third plurality of openings 2404 to form a second via layer V1 and an overlying second metal wire layer M2. The second metal wire layer M2 comprises a first transmission electrode 520 a′ and a first receiver electrode 522 a′. The first transmission electrode 520 a′ is laterally separated from the first receiver electrode 522 a′ by way of the third ILD layer 510. In some embodiments, the third metal material 2408 (e.g., copper) may be deposited by way of a deposition process, a subsequent plating process, and a CMP process, as described above.

Although FIG. 24 illustrates the formation of the second via layer V1 and second metal wire layer M2 using a dual damascene process, one of ordinary skill in the art will appreciate that the in alternative embodiments, the second via layer V1 and the second metal wire layer M2 may be formed using a single damascene process. In such embodiments, a first dielectric layer is selectively etched to form via holes, which are subsequently filled. A second dielectric layer is then formed over the first dielectric layer. The second dielectric layer is selectively etched to form metal trenches.

FIG. 25 illustrates some embodiments of cross-sectional views, 2500 and 2502, of an integrated chip corresponding to acts 2012-2018.

As shown in cross-sectional view 2500, a fourth ILD layer 512 is formed over the third ILD layer 510. The fourth ILD layer 512 is selectively exposed to a fourth etchant 2502 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the fourth ILD layer 512 to form a dielectric waveguide opening 2504. The dielectric waveguide opening 2504 comprises an oblong opening that laterally extends from a first position overlying the first transmission electrode 520 a′ to a second position overlying the first receiver electrode 522 a′.

As shown in cross-sectional view 2506, a dielectric material 2508 is formed within the dielectric waveguide opening 2504. The dielectric material 2508 comprises a higher dielectric constant than the surrounding ILD layers (e.g., ILD layer 510 and 512). In some embodiments, the dielectric material 2508 may be formed by way of a vapor deposition technique (e.g., PVD, CVD, PE-CVD, etc.) to a thickness that fills the dielectric waveguide opening 2504. A chemical mechanical polishing (CMP) process may be used to remove excess of the dielectric material 2508 from a top surface of the fourth ILD layer 512.

As shown in cross-sectional view 2510, the fourth ILD layer 512 is selectively exposed to a fifth etchant 2512 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the fourth ILD layer 512 to from a second plurality of via holes 2514. The second plurality of via holes 2514 comprise substantially round via openings disposed over an underlying metal layer (i.e., the via holes 2514 are predominately over the underlying second metal layer M2 so as to provide for contact between a subsequently formed via and the underlying second metal layer M2). The second plurality of via holes 2514 are laterally separated from the dielectric waveguide opening 2504 (i.e., the dielectric waveguide opening 2504 is disposed on a same vertical level as the second plurality of via holes 2514).

As shown in cross-sectional view 2516, a fourth metal material 2518 is formed within the second plurality of via holes 2514. In some embodiments, the fourth metal material 2518 (e.g., copper) may be deposited by way of a deposition process, a subsequent plating process, and a CMP process, as described above.

FIG. 26 illustrates some embodiments of cross-sectional views, 2600 and 2606, of an integrated chip corresponding to act 2020.

As shown in cross-sectional view 2600, a fifth ILD layer 518 is formed over the fourth ILD layer 512. The fifth ILD layer 518 is selectively exposed to a sixth etchant 2602 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to etch the fifth ILD layer 518 to from a fourth plurality of openings 2604 comprising metal trenches that extend through the fifth ILD layer 518.

As shown in cross-sectional view 2606, a fifth metal material 2608 is formed in the fourth plurality of openings 2604. In some embodiments, the fifth metal material 2608 (e.g., copper) may be deposited by way of a deposition process, a subsequent plating process, and a CMP process, as described above. The fifth metal material 2608 forms a second transmission electrode 520 b′ and a second receiver electrode 522 b′ within a third metal wire layer M3. The second transmission electrode 520 b′ is laterally separated from the second receiver electrode 522 b′ by way of the fifth ILD layer 518.

Therefore, the present disclosure relates to an integrated chip comprising differential coupling elements configured to couple electromagnetic radiation having a frequency outside of the visible spectrum from a silicon substrate into an integrated dielectric waveguide overlying the silicon substrate.

In some embodiments, the present disclosure relates to an integrated chip. The integrated chip comprises an inter-level dielectric (ILD) material disposed over a semiconductor substrate, and a dielectric waveguide disposed within the ILD material. The integrated chip further comprises a differential driver circuit configured to generate a differential signal having a first transmission signal component at a first output node and a complementary second transmission signal component at a second output node. The integrated chip further comprises a first transmission electrode located along a first side of the dielectric waveguide and configured to receive the first transmission signal component from the first output node, and a second transmission electrode located along a second side of the dielectric waveguide and configured to receive the complementary second transmission signal component from the second output node.

In other embodiments, the present disclosure relates to an integrated chip. The integrated chip comprises a dielectric waveguide having a substantially rectangular cross-sectional is disposed within an inter-level dielectric (ILD) material arranged over a silicon substrate. The integrated chip further comprises a first metal interconnect layer disposed along a first side of the dielectric waveguide and a second metal interconnect layer disposed along a second side of the dielectric waveguide. The first metal interconnect layer has a first transmission electrode coupled to a first output node of a differential driver circuit and a spatially separated first receiver electrode coupled to a first input node of a differential receiver circuit. The second metal interconnect layer has a second transmission electrode coupled to a second output node of the differential driver circuit and a spatially separated second receiver electrode coupled to a second input node of the differential receiver circuit.

In yet other embodiments, the present disclosure relates to a method of forming an integrated dielectric waveguide. The method comprises forming a differential driver circuit within a semiconductor substrate, wherein the differential driver circuit comprises a first output node configured to provide a first transmission signal component and a second output node configured to provide a complementary second transmission signal component. The method further comprises forming a dielectric waveguide within an inter-level dielectric (ILD) material overlying the semiconductor substrate. The method further comprises forming a first transmission electrode located along a first side of the dielectric waveguide and configured to receive the first transmission signal component from the differential driver circuit. The method further comprises forming a second transmission electrode located along a second side of the dielectric waveguide and configured to receive the complementary second transmission signal component from the differential driver circuit.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. An integrated chip, comprising: an inter-level dielectric (ILD) material disposed over a semiconductor substrate; a dielectric waveguide disposed within and surrounded by the ILD material; a differential driver circuit configured to generate a differential signal having a first transmission signal component at a first output node and a complementary second transmission signal component at a second output node; a first metal interconnect wire located along a first side of the dielectric waveguide and configured to receive the first transmission signal component from the first output node; and a second metal interconnect wire located along a second side of the dielectric waveguide and configured to receive the complementary second transmission signal component from the second output node.
 2. The integrated chip of claim 1, further comprising: a third metal interconnect wire located along the first side of the dielectric waveguide and separated from the first metal interconnect wire; a fourth metal interconnect wire located along the second side of the dielectric waveguide and separated from the second metal interconnect wire; and a differential receiver circuit configured to receive a first received signal component from the third metal interconnect wire and to receive a complementary second received signal component from the fourth metal interconnect wire.
 3. The integrated chip of claim 1, wherein the first metal interconnect wire and the second metal interconnect wire are mirror images along a plane bisecting the dielectric waveguide.
 4. The integrated chip of claim 1, wherein the differential driver circuit comprises: a first MOS transistor having a first drain region coupled to the first metal interconnect wire, a first gate structure configured to receive a first input signal, and a first source region coupled to a ground terminal; and a second MOS transistor having a second drain region coupled to the second metal interconnect wire, a second gate structure configured to receive a second input signal, and a second source region coupled to the ground terminal.
 5. The integrated chip of claim 1, further comprising: a first plurality of metal interconnect wires that are spaced apart from one another along the first side of the dielectric waveguide; and a second plurality of metal interconnect wires that are spaced apart from one another along the second side of the dielectric waveguide.
 6. The integrated chip of claim 5, wherein the first plurality of metal interconnect wires are electrically coupled to the first output node of the differential driver circuit.
 7. The integrated chip of claim 5, wherein the first plurality of metal interconnect wires are electrically decoupled from one another, and the second plurality of metal interconnect wires are electrically decoupled from one another.
 8. The integrated chip of claim 7, further comprising: a plurality of driver circuits configured to receive first and second input signals and to generate a plurality of differential signals; and wherein the plurality of driver circuits are respectively coupled to one of the first plurality of metal interconnect wires and one of the second plurality of metal interconnect wires.
 9. The integrated chip of claim 5, wherein two or more of the first plurality of metal interconnect wires are different sizes.
 10. The integrated chip of claim 1, wherein the dielectric waveguide comprises silicon nitride (SiN) or silicon carbide (SiC).
 11. The integrated chip of claim 1, wherein the first metal interconnect wire and the second metal interconnect wire comprise copper.
 12. An integrated chip, comprising: an inter-level dielectric (ILD) structure disposed over a substrate; a dielectric waveguide disposed within and surrounded by the ILD structure; a differential driver circuit having a first output node configured to output a transmission signal component and a second output node configured to output a complementary transmission signal component; a first copper interconnect wire arranged within the ILD structure along a first side of the dielectric waveguide and coupled to the first output node; and a second copper interconnect wire arranged within the ILD structure along a second side of the dielectric waveguide and coupled to the second output node, wherein the first and second sides are different faces of the dielectric waveguide.
 13. The integrated chip of claim 12, further comprising: a third copper interconnect wire located along the first side of the dielectric waveguide and separated from the first copper interconnect wire by the ILD structure; a fourth copper interconnect wire located along the second side of the dielectric waveguide and separated from the second copper interconnect wire by the ILD structure; and a differential receiver circuit having a first input node coupled to the third copper interconnect wire and a fourth input node coupled to the fourth copper interconnect wire.
 14. An integrated chip, comprising: a dielectric waveguide disposed within and surrounded by an inter-level dielectric (ILD) material arranged over a silicon substrate; a differential driver circuit configured to provide a first signal component of a differential signal at a first output terminal and a complementary second signal component of the differential signal at a second output terminal; a first metal interconnect layer comprising a first transmission electrode disposed along a first side of the dielectric waveguide and coupled to the first output terminal of the differential driver circuit; and a second metal interconnect layer comprising a second transmission electrode disposed along a second side of the dielectric waveguide and coupled to the second output terminal of the differential driver circuit, wherein the first and second sides are different outer surfaces of the dielectric waveguide.
 15. The integrated chip of claim 14, wherein widths of the first transmission electrode and the second transmission electrode are tapered from a first width to a second narrower width in a first transition region overlying the dielectric waveguide.
 16. The integrated chip of claim 14, wherein a width of the dielectric waveguide is tapered from a third width to a fourth narrower width in a second transition region underlying the first transmission electrode.
 17. The integrated chip of claim 14, wherein the dielectric waveguide comprises silicon nitride (SiN) or silicon carbide (SiC).
 18. The integrated chip of claim 14, wherein the differential driver circuit comprises: a first MOS transistor having a first drain region coupled to the first transmission electrode, a first gate region configured to receive a first input signal, and a first source region coupled to a ground terminal; and a second MOS transistor having a second drain region coupled to the second transmission electrode, a second gate region configured to receive a second input signal, and a second source region coupled to the ground terminal.
 19. The integrated chip of claim 14, wherein the first metal interconnect layer further comprises a first receiver electrode disposed along the first side of the dielectric waveguide and spatially separated from the first transmission electrode.
 20. The integrated chip of claim 14, further comprising: a first plurality of transmission electrodes disposed above the dielectric waveguide and coupled to one or more first output terminals of the differential driver circuit; and a second plurality of transmission electrodes disposed below the dielectric waveguide and coupled to one or more second output terminals of the differential driver circuit. 